1. Technical Field
The present invention relates to a terminal device connected to a network, a printing system including the terminal device, and a control method of the terminal device.
2. Description of Related Arts
Power-saving functions of electrical equipments such as printers and MFPs (Multiple Functional Peripherals) are attracting more acute attention from the viewpoint of manufacturers' and users' social responsibilities. In particular, industrialized countries have implemented various procurement regulations which require public institutions to evaluate power-saving capabilities of electrical equipments (e.g. Laws on Promoting Green Purchasing) as well as various distribution regulations (e.g. Directive on Eco-Design of Energy-using Products), in order to ensure that products without a certain level of power-saving capabilities will be removed from the market.
For the purpose of striking a balance between power-saving functions and usability features, a latest control method of a printer or MFP includes steps of switching the printer/MFP into a power-saving mode when its standby mode has passed a certain period of time, and restoring the printer/MFP to a normal mode when it receives a network packet. For example, the Japanese Unexamined Publications No. H09-141974, No. 2002-278378, and No. 2004-110215 propose an image forming device which capable of shutting down the CPU of its printer controller, or lowering clock frequencies of the CPU to shift the printer controller into a power-saving mode. This control method is generally called “WOL” (Wake on LAN).
A network printer generally receives various network packets including printing requests and status inquires as it serves a large number of network devices. In this respect, a WOL-capable network printer needs to be associated with suitable recovery packets to its operating environment so that it can properly recover from a power-saving mode to a normal mode. For example, under a network environment involving frequent status inquiries in SNMP (Simple Network Management Protocol, Well-known Port=161), the printer can hardly maintain its power-saving mode if an SNMP packet is designated as a recovery packet. Therefore, a SNMP packet should not be designated as a recovery packet under such a network environment as described above. Nowadays, a WOL-capable NIC (Network Interface Card) is generally equipped with sophisticated packet selection functions in order to select a suitable recovery packet.
Incidentally, packet transmission under in IP/Ethernet that is known as the most common LAN environment for corporate or domestic use, requires a combination of IP address and MAC address of the transmission destination. The combination of IP address and MAC address is normally stored in a data area called ARP (Address Resolution Protocol) table within a terminal device. If MAC address of the packet destination does not exist in the ARP table, an ARP request needs to be issued for the purpose of inquiring the MAC address corresponding to the IP address of the packet destination. However, an entry of the ARP table will generally be lost in a certain period of time after its registration (e.g. several minutes)
The lost entry from the ARP table will necessitate an ARP request preceding each packet transmission afterwards. However, an ARP requests should not be designated as a recovery packet as a typical printer cannot respond to an ARP request while in a power-saving mode. This causes a problem of frequent interruption of the power-saving mode due to the ARP request preceding each periodic packet such as an SNMP request (See FIG. 9).
The present invention is intended to solve the aforementioned problems in the prior art, and one of the objectives of the present invention is to provide a terminal device which can avoid the interruption of a printer's power-saving mode due to the ARP request preceding each periodic packet including a status inquiry in SNMP, a printing system including the terminal device, and a control method of the terminal device.